Meddling
by Madame Cross Marian
Summary: The first thing Mephisto Pheles noticed about his new sister was that she was heartbreakingly adorable. The second thing he noticed was that this was a very, very big problem. In which Mephisto and Co. slowly go mad in an attempt to subtly (or not so subtly, depending on who you ask) protect their only sister from literally everything. But especially boys. Fem!Rin
1. Chapter 1

The first thing Mephisto Pheles noticed about his new sister was that she was heartbreakingly adorable, to an extent that put all of his beloved moe characters, he was mourn to admit, to shame.

The second thing he noticed was that this was a very, very large problem.

Not now, of course, he had mused as he watched the small child in her first few minutes of life somehow manage to start earning her place as the apple of his eye, not yet. For now, for the next few years, she would be just that- adorable. It was to be expected, after all. Not only was the girl's mother beautiful above most humans in the world, but even if she hadn't been, all children of the royal blood line came out remarkably attractive. It was part of who they were, and how they emodied seduction to all sorts of different things, physical or no. Seduction to sins. But seduction was exactly the problem he saw awaiting him less than even two decades down the line, curse humans and their ridiculous growth rates!

For even now, he could see all to clearly: Rin Okumura was going to be quite the looker when she grew up. And lookers attracted... _boys._ And he could not let that stand.

All of these thoughts were kept strictly internal, of course, it wouldn't do to have Fujimoto knowing he may truly care for the child, and on the outside he continued to play the detached cynic, using this as a chance to make a wager he knew would end in his favour. The moment she unlocked her powers, her gaurdianship would immediately transfer over to him. He estimated this should take a decade at most, even with her power sealed away in kurikara. Satisfied that Fujimoto would, at the very least, keep her from dying or becoming horribly disfigured in the meantime, set off on his merry way, with dark, dark plans already forming in his mind. For her own good, of course.

* * *

"Allow me to make certain that we are on the same page here, Okumura." The man, if he was to be considered that, stated with deadly calm from his place beside the grave of Shiro Fujimoto. The human twin raised an eyebrow with well-deserved caution, and he thought, for a moment, that perhaps it wasn't the greatest of ideas to discuss such things with someone so likely to report back to his beloved sister at the drop of a hat. Then he remembered that he could just threaten him with death and violence. Or worse- expulsion. He didn't have to mean the threats- Yukio would believe him.

"I was most distressed yesterday, you see, as I came to execute your sister. Because, and do forgive my candor, I believe Miss Okumura was wearing..." The demon paused for dramatic effect. "Mascara? And I thought, surely this couldn't be correct, because, what good, religious household allows a CHILD to wear beauty products? A child who, mind you, is very clearly attractive on an unearthly level without such enhancements, and then you allow her to go and do, do... _that_? Do you know what happens to pretty girls, Okumura? They attract boys. Disgusting, filthy, _unworthy_ boys. So then I thought, well, surely this is some mistake? Surely neither of us want such a tragedy as for our beloved relation to be seduced by a male _creature?_ Surely her brother, who loves her dearly and should wish at all costs to prevent such a scenario for fear of both her safety and his life, would surely remove all such items from her possession in an inconspicuous manner from this point forth? _Surely?"_

He was expecting an initial refusal, or, at least, a reluctance on behalf of the younger twin, but when the child's blue eyes met his through rain spotted lenses, he could tell that, for the first, and possibly last time in either of their lives, they had found a point of agreement.

* * *

"What the HELL?" The cry wailed from the upstairs bathroom at the monestary. The shrillness of it was enough to make him wince, but Yukio knew that was the price he had to pay to carry out his duty. And if the garbage that morning happened to contain a little more mascara and blush than usual, he certainly wasn't going to point it out.

"What's wrong, sister?" He called innocently. "Stop fussing about whatever it is and hurry up! Sir Pheles is going to be here to pick us up any minute now."

With the old bathroom door locked firmly shut, she never saw her brother's triumphant smile as he turned away and headed towards the stairs that would lead him to his, as of this moment, only remaining comrade in the war to keep Rin single.

* * *

 **AN: Well, I feel that this was not terrible enough that some of you might enjoy it, so here it goes! And also a Happy Thanksgiving to everyone, of course. I may or may not update ever again**


	2. Chapter 2

Rin Okumura had always found it odd and, dare she say, almost suspicious that any boy who showed the slightest of interest in her would miraculously become terrified of her within a week's time. It was almost as though some demonic presence had been watching her from birth just to be certain that he could ward off the slightest chance of her ever having a relationship. Initially, this demonic force was Mephisto.

Being a very busy demon with important demon things to do, he, much to his dismay, had managed to let a few fortunate suitors (if six year olds could be called suitors) slip through the cracks. But as she grew older, and her human brother became more and more aware of how his beloved sister seemed to attract the bad boys like Sir Pheles to an anime convention, their combined evil powers seemed to succesfully lock her out from all non-relational male contact. In fact, with this new revelation of her heritage, she was finding it hard to doubt that her brother didn't somehow inherit selective Satantic powers which arose only at the possibility of her finding a date, and at no other time.

Up to that moment, his had been the only presence which she was securely aware of. But that all changed when she walked into the orientation hall of True Cross Academy and noticed that her uniform was a little... _different_ than all the other girls. About thirteen inches of different, in fact. Whereas the other girls all wore skirts falling somewhere around mid-thigh, depending on height, her tea-length skirt brushed innocently against the middle of her calf, none the wiser to the problem it was about to cause.

"Yukio."

"Yes." Her twin answered dutifully with the look of a soldier who knew he was about to be cut down, but was ready to die for his cause nonetheless.

"Do you have anything to do with this."

"...I don't even know what you mean, sister."

"Don't you play dumb, smart guy!"

"Well would you look at the time, I'm terribly sorry for whatever's troubling you, but I really mujst going, got speeches to deliver and all so-" He dashed out while he still had the chance, leaving the girl alone to find a seat in a sea of high-school shoujo skirts.

"That. DICK!"

* * *

It.

Was.

So.

CUTE.

She stared at the fluffy Scottie before her with unadulterated awe.

"Well helLO!" She cooed in her finest puppy voice. "Who's a pretty baby? Who's a pretty baby?"

The dog wagged it's tail in what she assumed to be approval, as well as giving her smug look that seemed to agree "yes, me, I am a pretty baby", before turning tail and trotting in the opposite direction.

"Wait a second, where are you going, huh?" She whined, following without hesitation.

When they got a suitable distance from the mosh of students, she added the puppy turning into the clown to the long list of disappointments in her life.

"Soft spot for animals, Princess?" The once-dog-now-human shaped school master jested.

"Yeah, real ones, ya freak!" She fumed.

"Well, I am the headmaster of this school, I couldn't very well just be wandering amongst the common folk, now could I?"

She only raised a delicate black-blue eyebrow, pale arms folded over her chest.

"And anyhow, I have important information to share with you regarding your exorcist training."

"Ah, no, hold on a second!" She interjected, unwilling to allow this man to continue without addressing the most pressing issue at hand. "What the HELL is up with my skirt, hm?"

"...A finely dyed linen, imported from the Middle East?"

"The _length_ of my skirt."

Damn her for not being an imbecile.

"Let's think about this rationally, my dear," he drawled, putting on his finest charm. "With those other skirts being so ridiculously short, wherever would you have hidden your tail? As a member of the demonic royal family, the idea alone of you parading about with your tail bared for the world to see, why, I couldn't bare it! How could I allow you to be so classless? The idea of you going on missions and being mistaken by filthy, low level demons as a common whore, when you are are the very princess of Gehenna- why, my heart couldn't take it!"

"Oh," she blinked up at his half-truth. "I guess that makes sense."

"Of course it does!" He internally breathed a sigh of relief. "If anyone asks, just say that your strict religious upbringing led you to seek special permissions about the uniform."

"Yeah, that works!" She grinned up at him with something akin to gratitude and for a moment he thought his heart would melt. Thankfully, he remembered, he didn't have one. What a close call. "Thanks, Mephisto. See, you're not so bad, ya know that?"

"Oh, yes of course," he murmured absently, struggling to keep the pink of his awe off his cheeks. She was just so cute, and sweet, and pure, and... _defendable._ His own real life tsundere! How lucky was he? "Anyhow, back to the truly important things, I will now show you to the exorcist cram school!"

"A cram school?" She let out in a whine.

"Yes, the exorcist cram school! You will begin as a page, learning the art of exorcism. Your lessons in the primary school don't begin until tomorrow, but your exorcist training begins today!" He waved his hand in a flourish for dramatic effect. "I will take the honor of showing you there immediately. However!"

She flinched as his hand swung out to point scarcely an inch from her face. He resisted the ever so tempting "boop" to her delicate nose, as easy and adorable as it would be, as somehow he found that may make her take his following words less seriously. His restraint was admirable. "Your identity as the daughter of Satan is to be kept and absolute secret! Now, while your tail is already concealed by the skirt as a proper gentle-demon, and your ears and teeth may be explained away, your flames are a different matter. You must keep them under only the strictest control."

A firm line formed over her delicate face that didn't quite succeed in being a serious grimace. "I'll do my best."

He considered her for a moment- considered her eyes that were so superficially similar to their father's, yet set in a genuine expression few had ever known from the original. Very nearly human. Nearly- but something new. "Very well, princess." He spun with a snap, already moving towards their destination. "However I can't help but remain a tad concerned, so I'll be personally monitering this first lesson nonetheless."

This, of course, had nothing to do with staking out the male reaction to her presence in the classroom, or to judge Yukio's worthiness in handling any such reactions. Nothing. At. All.

"Eins, zwei, drei!"

And with that, he was a dog yet again.

* * *

AN: Woooo, I updated! Hope y'all liked it :) I'm open to any constructive criticism in the comments as always, just because I do these for fun doesn't mean they get to be bad. For those wondering, of course Amaimon will be joining in once he shows up, just be patient xD


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